Foot-and-mouth disease (FMD), the most serious disease among the class A infectious diseases in animals, is a fulminating infectious disease which severely affects cloven hoofed animals such as pig, cattle, sheep and the like. Recently, livestock industries of many countries have suffered huge economical losses caused by the outbreak and epidemic of FMD. So far, seven serotypes of foot-and-mouth disease virus (FMDV) (European A, O and C, African SAT1, SAT2 and SAT3, and Asia 1 serotypes) and many subtypes (see, e.g., Kleid et al., 1981, Science 214: 1125-1129) have been known, with O serotype FMDV being the most widely spread serotype.
FMDV belongs to the Aphthovirus genus of the Picornaviridae family. It consists of a positive-sense, single-stranded RNA genome (about 8.5 kb) surrounded by 60 copies of three capsid viral proteins (VP1, VP2, and VP3). Investigations show that in FMDV serotype O, VP1 of these three viral proteins is most relevant to the infectivity of the virus. There are two immunogenic regions in VP1 protein, namely those portions of amino acid residues 141-160 and 200-213. They reside respectively in two protruding, disordered and highly mobile loop structures. The loop structure of the region of residues 145-157 comprises a conserved structure Arg-Gly-Asp (RGD region), involving in the attachment to cell surface receptors (Belsham G J and Martinez-Salas E, Genome organization, translation and replication of foot-and-mouth disease virus RNA, p. 19-52, 2004, Foot and Mouth Disease Current Perspectives, Edited by: Sobrino F and Domingo E). Protein 3D is a RNA-dependent RNA polymerase in FMDV, which has antigenic epitopes recognized by porcine T cells (Belsham G J and Martinez-Salas E, Genome organization, translation and replication of foot-and-mouth disease virus RNA, p. 19-52, 2004, Foot and Mouth Disease Current Perspectives, Edited by: Sobrino F and Domingo E).
Prophylactic immunization can control the transmission of FMDV. Killed virus is used in the existing anti-FMDV vaccines. In practice, such vaccines may cause the transmission of the disease due to the in vivo recombination of the viral RNA (Brown, F. An overview of the inactivation of FMDV and the implications when residual virus is present in vaccines. Dev Biol Stand 1991; 75: 37-41). Meanwhile, chemical inactivating agents are used to inactivate the virus in such vaccines, and low-temperature cold-chain transportation and freezer storage are required during delivery. No freezers are available in the rural areas of some developing countries, and consequently, the vaccines may have substantially lost their efficacy at time of injection. Moreover, the possibility of live FMDV virus leakage during the manufacture process makes the production of such vaccines an unsafe factor for the environment.
The epitope-specific vaccine of the present invention can elicit an antibody response against FMDV in the vaccinated animals. The vaccine of the present invention is not only very safe in use and production, but also very convenient in its handling, storage and transportation. Meanwhile, the vaccine of the present invention can be designed to meet specific requirements.